Optical receivers (or opto-receivers) measure light used in various applications such as atmospheric studies, laser rangefinding, and spot tracking. In many applications it is desirable to utilize the value of light flux over a wide dynamic range. For example, a target tracking (spot-tracking) device may provide directional information to a target by means of splitting a light spot reflected off of a target between four quadrants of a multi-sector photodetector. The distribution of light between the four quadrants of the photodetector provides an indication of how far "off-center" the detector is aimed. The light flux varies over a wide dynamic range as the tracker approaches the target, yet measurements must be taken.
The requisite wide-dynamic range has been achieved in the past by using gain-switched or logarithmic amplifiers. These designs are complex and difficult to implement without increasing the preamplifier noise. Further, these designs may be bulky and large, making them less desirable for use in airborne applications where size and weight are of paramount importance.
The following patents, incorporated by reference herein, generally disclose detecting and/or measuring light, especially laser light: U.S. Pat. Nos. 4,792,230 (measuring ultra-short optical pulses); 4,721,385 (FM-CW laser radar system); 4,830,486 (frequency modulated laser radar); 4,856,893 (which discloses both CW and pulse lasers, as well as range measurement); 4,812,035 and 4,846,571 (AM-FM laser radar).